Influence of the carbohydrate moiety on rotational correlation time and hydrodynamic volume of cow colostrum trypsin inhibitor

A large polysaccharide moiety of the cow colostrum trypsin inhibitor was removed by enzymatic cleavage; fully active protein was obtained by affinity chromatography. Rotational correlation times of the inhibitor labelled by dansyl chloride obtained from fluorescence depolarization measurements and hydrodynamic volumes from gel-permeation chromatography for protein with and without polysaccharide were compared with those of homologous Kunitz inhibitor. The mean rotational correlation time 105 ns and apparent mol. weight 16 000 were obtained for the colostrum inhibitor with polysaccharides; these values are considerably reduced to 44 ns and 8 700 dalton after removal of the polysaccharide moiety. For the pancreatic inhibitor an about four times shorter correlation time of 24 ns was obtained.